The object of the present invention is a method and a device for consolidating a geologic formation crossed by a deflected well by means of a substance which is polymerized in situ by injecting a gas. One possible application of the invention is the consolidation of deflected wells drilled through subterranean reservoir zones containing petroleum effluents brought into production.
The Oxpol and Thermopol processes (OXPOL and THERMOPOL are trademarks registered by the applicant), which are notably described in the French patents 2,474,558 and 2,575,500, are used to consolidate wells drilled in permeable geologic formations containing petroleum effluents. They are for example applied in producing wells crossing sandy zones and allow to stop sand advents.
The process mentioned above provides the consolidation of a permeable zone through the injecting of a polymerizable substance in situ which binds the non consolidated elements of a formation.
This substance can be a liquid mixture of organic products containing at least one polymerizable chemical compound and a catalyst, and this mixture can be polymerized in contact with an oxidizing gas (OXPOL process). The reaction starts at the normal temperature of the formation. It is exothermic and leads to the forming of a polymeric film which binds the unstable particles of the formation and makes it cohesive, without notably modifying the permeability thereof. The process is applied to vertical wells and comprises the successive injecting of the mixture and of the oxidizing gas, separated by a volume of a little oxidizable substance such as a solvent or a petroleum cut in order to prevent a premature reaction.
This substance may also be a mixture of liquid organic products likely to polymerize through a temperature rise (THERMOPOL process). This is achieved after introducing the mixture into the formation by the injection of a chemically inert hot gas.
With the previous techniques, the extent of the reaction can be controlled by adjusting the composition of the polymerizable mixture and the features of the reacting gas. The flow of gas passing through the volume to be consolidated eliminates the risks of clogging by the formed polymer.
The influence of gravity contributes to facilitating the implementing of the process in vertical wells or wells little inclined in relation to the vertical. It has a useful effect on the displacement of the injected constituents in order to obtain a good penetration into the formations to be plugged. The reacting gas injected after the organic mixture tends to remain above the mixture and, as seen above, a fluid volume is sufficient to maintain the separation and to prevent a premature reaction. The implementing of such a process in wells part of which is horizontal or almost horizontal presents particular difficulties because gravity has a less favourable effect for displacing the constituents and for separating the liquid mixture from the reacting gas.